and Diastrophism in Oceanica. 103 



the forms they now have. In their eyes, the physical evidence 

 in the areas of fragmentation, and especially in the southern 

 hemisphere, is not of a nature to compel the view that large 

 lands formerly existed here, and they say, further, that there 

 is no process in the mechanics of the earth known to them that 

 would account for such down-breaking of the lithosphere. 



Coleman in his presidential address of 19 15 8 holds firmly to 

 the theory of the permanency of oceans and continents. He 

 does not believe in a Gondwana Land across the Indian Ocean 

 uniting Africa to peninsular India. His belief is founded on 

 the knowledge that "the earth's crust over large areas . . . 

 approaches a state of isostatic equilibrium," and that "on the 

 broad scale continents are buoyed up because they are light, 

 and ocean bottoms are depressed because the matter beneath 

 them is heavy." In this we agree with Coleman. But he then 

 concludes : "There is no obvious way in which the rock beneath 

 a sea-bottom can be expanded enough to lift it 20,000 feet, as 

 would be necessary in parts of the Indian Ocean, to form a 

 Gondwana Land ; so one must assume that light rocks replace 

 heavy ones beneath a million square miles of the ocean floor." 



The fallacy of this conclusion is the assumption that the now 

 sunken parts of eastern Gondwana were raised out of the depths 

 of the Indian Ocean after it became very deep, i. e., seemingly 

 since the later Mesozoic and certainly not before Permian time. 

 The paleontologists, on the other hand, postulate the existence 

 of Gondwana at least as early as the Carboniferous, because 

 of the origin and wide distribution in the southern hemisphere 

 of the Glossopteris flora (Africa, India, Australia, Antarctica, 

 South America), and the writer has long been holding that the 

 origin of Gondwana goes back into Proterozoic time. It is 

 therefore not a question of raising Gondwana out of the realms 

 of Neptune and of buoying up its rocks and lessening their 

 specific gravity through expansion. These postulates are 

 unnecessary, for Gondwana has always been in existence since 

 there were oceans, or at least since the beginning of Paleozoic 

 time ; when the oceans began to deepen markedly in the earliest 

 Mesozoic and since then, these great sinking fields took into 

 themselves the above-mentioned sunken parts of Gondwana and 

 Australasia. 



Another, erroneous though less significant argument of Cole- 

 man's is that because "geodesists are demonstrating that the 

 earth's crust over large areas, and perhaps everywhere, 



8 A. P. Coleman, Dry land in geology, Bull. Geol. Soc. America, xxvii, 

 175-192, 1910. 



